  (function() {
  var b = document.documentElement,
  a = function() {
  var a = b.getBoundingClientRect().width;
  b.style.fontSize = 0.0625 * (640 <= a ? 640 : a) + "px"
},
  c = null;
  window.addEventListener("resize", function() {
  clearTimeout(c);
  c = setTimeout(a, 300)
});
  a()
})();